Method of making carbon commutators



Aug. 25, 1970 w. FORSTE ETAL 3,525,149

METHOD OF MAKING CARBON COMMUTATORS Original Filed April 5, 1968 2 Sheets-Sheet l \N'VENTORS WALTER FbRSTE e? 0| 8- 5, 1970 w. FORSTE ETAL 3,525,149

METHOD OF MAKING CARBON COMMUTATORS Original Filed April 5, 1968 2 Sheets-Sheet 2 FiG.7-

INV ORS WALTER F STE e? ol AGENT Patented Aug. 25, 1970 3,525,149 METHOD OF MAKING CARBON COMMUTATORS Walter Forste, Suhl, Thuringia, and Gottfried Ostermay, Berlin, Germany, assignors to VVB Elektrogerate, Berlin, Germany Original application Apr. 5, 1968, Ser. No. 719,071, now Patent No. 3,473,063, dated Oct. 14, 1969. Divided and this application Apr. 29, 1969, Ser. No. 840,886

Int. Cl. H01r 43/00 US. Cl. 29--597 3 Claims ABSTRACT OF THE DISCLOSURE Method of making carbon commutators for small electric motors, having an initially non-slotted carbon casing and an elongated supporting member therein, the electrical connecting elements for the armature windings being axially disposed between the casing and the member. A preferably hardenable and electrically conductive resin compound is provided in the casing for securing the same to the member and for immobilizing the connecting elements. After hardening of the compound, the casing is axially slotted so as to provide the required number of segments or lamellae as well as slots therebetween.

Two embodiments are disclosed, one having outer ribs on the supporting member while the other has a flanged terminal portion against which the casing abuts. The slots may also extend in the compound, to the outer surface of the member.

The invention relates to a method for establishing contact connections between the armature winding wires and the lamellae or segments of carbon commutators in small electric motors.

The state of the art features carbon commutators for small and very small machines or motors whose segments are made individually and are provided with slots or boreholes for receiving the wires. The contact connection between the wires and the commutator proper is established here after the latter has been assembled, and this is done by running the winding wires through the slots in the segments; afterward, the wires are corrugated or coiled and they are then run back into these slots or boreholes. In order to avoid tensions or wedging effects, the wires are attached in the slots by means of electrically conductive and hardening compounds or putties and the like.

One disadvantage here is that the electrical or mechanical connections between the wires and the segments, specially designed for this purpose, are established in several work operations; in other words, this is a timeconsuming and expensive method.

It is one of the main objects of this invention to reduce the time-consuming and expensive operations for the establishment of an electrical and mechanical connection between the winding wires and the segments or lamellae.

It is an object of the invention to create a durable, advantageously established combined electrical and mechanical connection by means of a suitable productionengineering method used in making the commutator body proper.

The invention, according to its major features, solves the problem as follows: A supporting member made of a suitable insulating material is arranged on the armature shaft; it is provided with technical means, for example, ribs or a flange, for centering a cylindrical carbon casing. The bared winding wires are distributed in axial symmetry around the circumference, between the supporting member and the casing, and they are attached with an electrically conductive, hardenable resin. The remaining spaces are simultaneously filled with this resin.

After the resin has hardened, the carbon casing is slotted radially with respect to the axis of the supporting member and the resin is preferably also slotted to the outer surface of the supporting member, thereby producing the segments or lamellae.

In the production method according to this invention, there is a major advantage. in that the carbon casing can be attached to the supporting member, and the winding wires can be connected to the casing, in a single operation. The wires being covered with a resin, their surfaces are protected against oxidation so that contact resistance is kept low.

Other important features of the invention will become apparent from the specification, together with those of the inventive method for making such carbon commutators. Objects, attendant advantages and further details of the invention will be readily appreciated as the same becomes better understood by reference to the following detailed description, when considered with the accompanying drawings, wherein FIG. 1 is a view of a three-segment commutator made according to the present invention;

FIG. 2 is "a side view of the commutator of FIG. 1, together with parts of the associated armature;

FIG. 3 is a longitudinal sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a transversal sectional view taken along line 4-4 of FIG. 2;

FIG. 5 is a view similar to that of FIG. 1 but of an S-segment commutator according to the present invention;

FIG. 6 is again a side view (the armature being omitted from this illustration) of the commutator of FIG. 5;

FIG. 7 is a longitudinal section view taken along line 7-7 of FIG. 5; and

FIG. 8 is a transversal sectional view taken along line 88 of FIG. 6.

As a matter of example, a three-segment commutator is shown and described with respect to FIGS. 1 to 4, relating to a first exemplary embodiment, although, it will be understood, the principles apply to other numbers of segments, slots therebetween and appropriate connecting wires for the armature windings. The latter will not be described or illustrated since it is well known to those skilled in the art. An 8-segment alternative will be described later with respect to the remaining FIGS. 5 to 8.

Once the armature assembly has been assembled, it is pushed over and attached in the conventional manner on a shaft 2. No details being described, the armature is generally designated by numeral 4. It may of course be treated or immersed in lacquer in the usual manner. At the point of the shaft 2 where the commutator should be provided a substantially cylindrical supporting member 6 is attached, as best shown in FIG. 3. The member is preferably made from an insulating plastic material. On the surface member 6 is provided with axial ribs 22, as visible in FIGS. 1 and 4, corresponding in number to the segments or lamellae.

A non-slotted carbon cylinder or casing is pushed over the supporting member 6, as shown in FIG. 3; it is substantially centered by the ribs 22. The lengths of these elements are substantially the same. Numerals 18 and 20, to be described later in detail, apply to the carbon casing. The spaces between the casing and the member 6 and its ribs is filled up with a preferably electrically conductive, preferably hardenable resin compound shown at 16; such a compound can be heat-treated and hardened, or otherwise solidified, so as to lend a certain degree of stability to the assembly, as will be expalined in more detail.

In the afore-mentioned spaces, winding connecting elements 12 or 14 are axially inserted, the former constituting metal foils or strips while the latter may be wires which can be soldered or otherwise attached with their ends to the strips 12, as indicated in FIG. 2. It will be understood that either the strips 12 or the wires 14 themselves can be inserted in the spaces between the casing and the member 6.

The subassembly is then hardened, and then the casing is longitudinally slotted, in a direction radially toward the shaft 2, whereby segments or lamellae 18 are obtained, interspersed with a corresponding number of slots 20, as shown in FIGS. 1, 2 and 4. In the example shown in these figures, three segments are formed with three slots therebetween. The ribs 22 separate the conductive sections of the resin 16, as shown in FIG. 1, thereby providing the required insulation between the electric connections.

This construction has proven to be simple and efficient in production. Deviations of the measurements of the casing and the member are eliminated by the provision of the compound or resin poured into the spaces therebetween. It will be understood from the preceding description that the commutator can be manufactured in a cheap and expeditious manner, without resorting to multiple steps and using complicated jigs and the like. The contact between the armature-winding wires, or connecting strips, and the segments of the casing are both mechanically and electrically ensured by the provision of the conductive compound.

It is particularly advantageous that the attachment between the carbon casing and the supporting member, as well as that between the connecting elements and the embedding compound is accomplished in a single procedural step.

We are now coming to the 8-segment alternative of the invention, shown and described with respect ot FIGS. 5 to 8, relating to a modified or second examplary embodiment. Only those features which are different from the first embodiment will be explained in detail. It should be noted that FIGS. 5 to 8 substantially correspond in their showing to the respective preceding figures (namely, FIGS. 1 to 4) with the only dilference that in FIG. 6 the armature assembly has been omitted for the sake of clarity.

Shaft 2 of the first embodiment has its counterpart in shaft 2A of FIGS. 5 to 8; similarly, elements 12A, 16A, 18A and 20A are identical with or closely similar to the respective elements 12, 16, 18 and 20 described earlier.

The manufacturing procedure is much like that by which the first embodiment is made. In the second emmodiment, a supporting member 6A is provided which does not have the previously described ribs but has a terminal, flanged portion 26A as best shown in FIGS. 6 and 7. The casing is pushed over the member 6A so that it abuts against the portion 26A and is substantially centered thereon. It should be noted that the diameter of the non-slotted carbon cylinder or casing is larger than that of the center or main portion of the member 6A, the space therebetween being filled up with the compound or resin 16A.

The metal strips 12A or connecting wires 14A are axially embedded in the compound which again provides electrical connection to the respective segments 18A. In the modified or second embodiment, there are eight segments and a corresponding number of connecting elements 12A.

Here, again, the casing is longitudinally slotted once the subassembly is hardened. It should be noted however that in making the radially inwardly directed slots the compound or resin 16A is also sloted, as shown in FIGS. 5 and 8, all the way to the outer surface of the main portion of the member 6A.

The advantages of the second embodiment are similar to those of the first one, as explained hereinabove.

A similar invention is described in applicants co-pending patent application Ser. No. 835,851, filed on the same day, and entitled Method of Making Carbon Commutator,, both applications being respective divisionals of Ser. Nos. 719,070 and 719,071, now US. Pats. 3,473,062 and 3,473,063 of Oct. 14, 1969, describing alternative features which, however, can be combined with those disclosed and claimed herein.

What We claim is:

1. A method of making carbon commutators for small electric motors having an armature, windings thereon, and electrical connecting elements for said windings; the method comprising the steps of (a) pushing a cylindrical carbon casing about an elongated supporting member;

(b) axially disposing at least tWo of said connecting elements in the space between said caing and said member;

(c) providing an electrically conductive hardenable compound in said casing for securing the same to said member and immobilizing said connecting elements;

(d) hardening said compounds; and

(e) axially slotting said casing so as to provide at least two substantially symmetrical segments therein and a corresponding number of slots between said segments.

2. The method as defined in claim 1, wherein said supporting member has axial outer ribs; further comprising the step of centering said casing about said ribs after said pushing step; and wherein said slotting step is performed only to the depth of the outer periphery of said ribs.

3. The method as defined in claim 1, wherein said supporting member has flanged terminal portion and said casing has a diameter larger than that of the main portion of said supporting member; and said slotting step is performed in said csing as well as in said compound, between said casing and said member, to the depth of the outer periphery of said main portion of the member.

References Cited UNITED STATES PATENTS 1,270,967 7/1918 Mizer 310-233 2,645,733 7/1953 Marsal 295-97 X 2,922,832 1/1960 Gottschall et a1. 264-104 X JOHN F. CAMPBELL, Primary Examiner C. E. HALL, Assistant Examiner US. Cl. X.R. 264-104, 272, 275

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 51 9 Dated ugust 25, 1970 Inventor(s) Fiirste et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The first inventor s name is correctly "Walter Fb'rste" as it appears in the earlier patents 5,475,062 and 5 (of which this is a divisional) while the inner and drawing headings erroneously indicate "W. Forste" Column 4, line 27 (that is, claim 1, eighth line) "caing" should read casing line 46 (claim 5, line 2) "has flanged" should read has a flanged and line 49 (claim 5, line 5) csing" should read casing;

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